A journalist who fell to his death from a fifth-storey window had received threats while preparing a report claiming Russia planned to provide sophisticated weapons to Syria and Iran, his newspaper said Tuesday.

Prosecutors have opened an inquest into the death of Ivan Safronov, a military affairs writer for the daily Kommersant. He died Friday in what some media said could have been murder.

The paper reported that Safronov had told his editors he would write a story about Russian plans to sell weapons to Iran and Syria via Belarus, but said he had not submitted the article.

Kommersant said Safronov recently told colleagues he had been warned he would face a criminal investigation on charges of revealing state secrets if he reported allegations that Russia had struck a deal to supply advanced Iskander missiles to Syria. Such a contract would upset the balance of forces in the Mideast and likely anger Israel and the United States.

Safronov did not say where the warning came from, according to Kommersant, but he had repeatedly been questioned in the past by the Federal Security Service or FSB, which suspected him of divulging state secrets in his reports. The FSB is the main successor agency to the KGB.

"Ivan Safronov said he was not going to write about it for a while, because he was warned that it would create a huge international scandal and the FSB would launch a criminal case on charges of breaching state secrets," the report said.

Russia's arms sales to such nations as Iran and Syria have been an irritant in its relations with the U.S. and have drawn criticism from Israel.

Ignoring U.S. and Israeli criticism, Russia has delivered 29 Tor-M1 mobile surface-to-air missile systems to Iran under a $700 million US contract. Russian news reports have said the Iranians were pushing Russia to sell much more potent, long-range S-300 air-defence missile systems.

Kommersant reported that, before his trip to an international arms fair last month in the United Arab Emirates, Safronov said he would try to confirm indications that Russia planned to sell S-300 missiles to Iran and Su-30 fighter jets to Syria via Belarus. Safronov later called his editors from Abu Dhabi and said he had received the necessary confirmation from Russian officials who attended the exhibit, Kommersant reported.

Upon his return from the trip, it said, Safronov told colleagues that he also had learned about Russian plans to provide Syria with Iskander missiles, MiG-29 fighter jets and Pantsyr-S1 air defence systems.

The Iskander, a sophisticated surface-to-surface missile with a range of 280 kilometres, would give Syria the capability to strike targets in Israel with high precision. Israel has complained about past sales of anti-tank missiles to Syria, saying that some landed in the hands of the militant group Hezbollah.

Russia has been plagued by attacks on reporters who seek to expose official corruption and other abuses. The problem was highlighted by the October killing of Anna Politkovskaya, an investigative reporter and a harsh critic of human rights abuses in Chechnya.

A report Tuesday from the Brussels-based International News Safety Institute listed Iraq, Russia and Colombia as the deadliest countries for journalists and their support staff.